ARM: stm32: Re-enable KS8851 on DHCOM

Since the KS8851 driver is now in, enable the Kconfig entry on DHCOM
to make the second ethernet available.
Signed-off-by: NMarek Vasut <marex@denx.de>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: NPatrick Delaunay <patrick.delaunay@st.com>

configs/stm32mp15_dhcom_basic_defconfig

@@ -101,6 +101,7 @@ CONFIG_SPI_FLASH_MTD=y
 CONFIG_SPL_SPI_FLASH_MTD=y
 CONFIG_DM_ETH=y
 CONFIG_DWC_ETH_QOS=y
+CONFIG_KS8851_MLL=y
 CONFIG_PHY=y
 CONFIG_PHY_STM32_USBPHYC=y
 CONFIG_PINCONF=y